1. Field of the Invention
The present invention relates to components and their methods of manufacture. More particularly, the invention pertains to micromechanical, microelectromechanical and microoptoelectromechanical components and their method of manufacture.
2. Description of the Prior Art
In order to minimize ambient influences such as moisture or contaminants (e.g. dust) on microelectromechanical components (MEMS) or microoptoelectromechanical components (MOEMS), the active structures of such components are often hermetically tightly encapsulated or sealed. (“Active structure” refers, in particular, to movable structures, optical structures or structures having both movable and optical components (e.g. movable mirrors). The term “active area” refers to the area or volume of the component in which the active structure lies or moves). The hermetically sealed encapsulation can also be employed to set a specific internal pressure in the region of the active structures. This is particularly advantageous for components whose functioning depends on a defined internal pressure, such as acceleration sensors and gyroscopes (rate of rotation sensors).
MEMS or MOEMS components are generally manufactured at the wafer level so that production can be as cost-effective as possible. The joining processes that are often required can be effected by direct bonding and anodic bonding processes.
Leading electrical contacts out of the hermetically sealed region to make contact with specific parts of the component (e.g. with the active structure) is difficult to accomplish. Various possibilities exist: the electrical contacts can be accomplished, for example, by laterally extending semiconductor layers produced by implantation or diffusion with low sheet resistance (see Reference 1 infra). Realization by patterned conductive layers covered with a planarized passivation layer is also possible.
As an alternative, electrical contacts in the form of a plurality of vertically extending plated-through holes can be led out of the component. To produce such holes, contact holes are first produced in the component, with conductive material subsequently introduced into the contact holes. The conductive material introduced into the contact holes may be, for example, metal deposited by vapor deposition, sputtering, electrodeposition or a CVD (chemical vapor deposition) process. The conductive material may also comprise some other material such as doped semiconductor (polysilicon). Before the conductive material is introduced into the contact holes, their inner walls are generally provided with an insulating material (e.g. SiO2, Si3N4, polyimide or the like) to prevent electrical short circuits with other conductive regions of the component.
The contact holes can be produced in various ways. Use is usually made of ultrasonic (References 2, 3), sandblasting (Reference 2) or water-jet-based drilling methods. The holes produced by drilling have diameters of hundreds of μm and are therefore only suitable to a limited extent for fabricating small MEMS or MOEMS components. Such drilling methods, furthermore, only partially meet clean room criteria. To avoid such disadvantages, it is known to fabricate the contact holes by laser beam drilling. Although such drilling avoids the abovementioned disadvantages, it often leads to material stresses or melting due to high temperatures. This poses problems during further processing of the component. For this reason, the forming of contact holes has been changed to chemical or plasma-chemical patterning.